Melanoma is one of the more common malignant tumors in clinical practice, and it is also one of the fastest growing malignant tumors with an annual growth rate of 3-5%. The annual number of new cases of melanoma around the world is 199,627, and the number of deaths is 46,327. Although the incidence of melanoma is low in China, it has multiplied in recent years. In China, the incidence in 2000 was merely 0.2/100,000, but the incidence in 2005-2007 was 1/100,000, and the annual number of new cases is about 20,000. Therefore, melanoma has become one of the diseases that seriously threatens the health of Chinese people.
Presently in China, the study of drugs for the treatment of this disease is still in the initial stages. The drugs Vemurafenib tablet and Ipilimumab (a monoclonal antibody) are useful for the treatment of melanoma, but these two drugs may cause other skin diseases, such as squamous cell carcinoma and the like, while exerting their activity. Therefore, it is of great importance to find effective drugs for the treatment of melanoma.
According to feedbacks from clinical studies, MEK kinase inhibitors have excellent efficacy against the “king of cancers”, i.e. advanced melanoma. Therefore, MEK kinase inhibitors have become a hot anti-cancer target, for which many major companies compete to develop.
The international patent application PCT/CN2014/085976 from the present applicant provides a MEK kinase inhibitor of the following formula, the chemical name of which is 2-((2-fluoro-4-iodophenyl)amino)-1-methyl-4-((6-methylpyridin-3-yl)oxy)-6-oxo-1,6-di hydropyridine-3-carboxamide. It was found that this compound has strong inhibitory activity against MEK kinase. It has the potential to be developed as a new drug for the treatment of melanoma, and provides a new therapeutic option for melanoma patients.

It is known by those skilled in the art that a compound in the form of a free base is usually pharmaceutically unacceptable due to defects in its properties. For most drugs, it is necessary to provide active compounds in other forms in order to improve these defects, and a common solution is to transform compounds in the free base form into pharmaceutically acceptable salts thereof. In addition, the crystal structure of the pharmaceutically active ingredient often affects the chemical stability of the drug. Different crystallization conditions and storage conditions can lead to changes in the crystal structure of the compound, and sometimes the accompanying production of other forms of crystal form. In general, an amorphous drug product does not have a regular crystal structure, and often has other defects, such as poor product stability, smaller particle size, difficult filtration, easy agglomeration, and poor liquidity. Therefore, it is necessary to improve the various properties of the above product. There is a need to find a new crystal form with high purity and good chemical stability.